(a) Technical Field
The present invention relates to a sealing apparatus for a foam injection mold, and more particularly to a sealing apparatus that seals a foaming space between a core and a skin in a foam injection molding machine that manufactures a product having a foaming layer between the core and the skin.
(b) Background Art
In general, crash pads that protect a passenger during a vehicle collision accident and the like are installed on front inner sides of a driver seat and passenger seat as interior materials installed on a front side of an interior of a vehicle. The crash pad is manufactured to have an appealing surface in terms of external appearance while showing a resiliently cushioning performance and a property of absorbing an impact, using a foam material.
Generally, a crash pad for a vehicle includes a skin which is a skin material that provides an appealing surface, and a core that operates as a frame of the crash pad on an inner side of the skin. A foam layer, such as a polypropylene (PP) foam layer, a polyurethane (PU) foam layer, and the like, that provides a cushioning performance and an impact absorbing performance is interposed between the skin and the base.
FIGS. 1A to 1D are exemplary views showing processes for manufacturing a crash pad according to the related art. A core 1 is formed through polymer injection molding, a skin 2 is formed through vacuum absorption, and a foam layer 3 is formed through foaming. The processes will be described below.
First, the core 1 is formed by injecting a polymeric resin material 1a into an injection mold including an upper mold 4 and a lower mold 5 (FIG. 1A), and the skin 2 preheated in a male vacuum-forming mold 6 is inserted into the injection mold to be formed through vacuum absorption (FIG. 1B). In particular, although not shown in the drawings, fine vacuum apertures for vacuum absorbing the skin 2 are formed in the vacuum forming mold 6, and the vacuum apertures are connected to one passageway in the mold, and then is connected to an external large capacity vacuum pump.
Further, after a foaming liquid 3a is injected onto a core 1 of the lower mold 5, the foaming upper mold 7 to which the skin 2 is attached is closed and the skin 2 attached to the upper mold 7 is pressed and bonded onto the foaming liquid 3a of the lower mold 5. Thereafter, the skin 2 and an unnecessary marginal portion (e.g., a portion formed by the leaked foaming liquid and the like) of the foam layer 3 are cut off and removed together (e.g., trimmed), and an outer portion of the skin 2 is surrounded by the foam layer 3 and is bonded and fixed to the core 1 using an adhesive.
However, since the core 1, the skin 2, and the foam layer 3 are formed separately in different molds, a total of three molds (e.g., core injecting-molding upper and lower molds, a vacuum-forming mold, and a foaming upper mold) are required, which increases investment costs such as mold costs and manufacturing costs.
Further, since an outer portion of a cavity is opened even when the lower mold 5 and the foaming upper mold 7 is closed, the foaming liquid may leak through the opened outer portion (e.g., an excessive loss of the foaming liquid and an increase in manufacturing costs may be caused). Further, as shown in FIG. 1D, after the manufacturing process is completed, a separate process of cutting off a marginal portion formed by the leaked liquid and a marginal portion of the skin 2 or cutting off only the leaked portion, surrounding the cut portion with an outer portion of the skin 2, and bonding the outer portion of the skin 2 to the cut portion may be necessary.
Further, since the foaming liquid should be injected into the opened cavity space (e.g., foaming space), a temperature of the injected foaming liquid should be controlled and maintained within a defined temperature range, which may be difficult. Further, a minimum thickness of the foaming layer 3 should be designed to a uniform thickness of a predetermined thickness (e.g., 5 mm) or larger due to an early solidification of the foaming liquid in a structure in which the foaming space is opened and the foaming liquid leaks, which lowers a degree of freedom of the crash pad.
To solve the above disadvantages, a molding apparatus in which a vacuum forming mold and a foaming upper mold are integrated in a common mold and an outer portion of a skin is attached to a core by a slide mold to seal a foaming space has been developed, thus reducing the number of molds, costs, and the cost price, and reduces an excessive loss of the foaming liquid, and improves a degree of freedom of design of the crash pad.
FIG. 2 is an exemplary schematic view showing a foam injection molding apparatus including a slide mold that prevents leakage of a foaming liquid according to the related art, and a crash pad can be manufactured through IMG foam injection molding in the shown crash pad manufacturing apparatus. In particular, an IMG (In-Mold Grain) foaming method refers to a method of forming an embossment (e.g., a protrusion or raised portion on the surface) on an inner surface of a mold (e.g., vacuum forming mold) to form a skin (e.g., formed of thermoplastic olefin (TPO)), and to form the skin through heating of the skin and suctioning of vacuum into a mold and forming an embossed shape (e.g., a raised shape) on a surface of the skin.
As shown, the core 1 is formed by injecting a resin into a mold while the core injecting molds 10 and 11 are combined with each other, and the skin 2 is vacuum absorbed in the vacuum forming mold 12 to be formed at the same time. Furthermore, the mold is rotated and fed by an upper rotation unit to combine the vacuum forming mold 12 in which the skin 2 is formed with the lower mold 11 in which the core 1 is formed, and then the foaming liquid is injected and foamed between the core 1 and the skin 2 to form the foam layer 3.
When the foaming liquid is injected, the slide mold 12a seals the foaming space by attaching a outer portion of the skin 2, and then the slide mold 12a moves forward by a distance suitable for sealing during the foaming operation and then is fixed to maintain the sealed state. The slide mold 12a moves rearward to eject a product after the foaming operation.
Furthermore, as shown in FIG. 3, the sealing operation is performed while a sealing boss 1c formed in the core 1 overlaps the skin 2, and thus the foaming liquid may be prevented from being leaked to the exterior of the mold by the sealing boss 1c. The molding apparatus prevents leakage of a foaming liquid to some degree, and shares a mold, thereby reducing the number of molds, mold costs, invest costs, and the cost price.
However, to prevent leakage of the foaming liquid, an amount of the overlapping portion between the sealing boss 1c and the skin 2 should be maintained at a predetermined level (e.g., 0.3 mm) or higher and no gap should be generated between the sealing boss 1c and the skin 2. However, due to mold tolerances “a” and “a′” and contractions “b” and “c” of materials indicated in FIG. 3, a gap may be generated between the sealing boss 1c and the skin 2. Accordingly, the foaming liquid is leaked in the foaming process thus, the foaming pressure and foaming amount may not be secured, and the leaked foaming liquid may be stuck to the mold, bonding the product to the mold, causing difficulty in the ejection of the product.